There is a need for reagents, kits and methods for screening, diagnosing and monitoring individuals with stomach or esophageal cancer, including metastasized stomach and esophageal cancer. There is a need for reagents, kits and methods for identifying and confirming that a cancer of unknown origin is stomach or esophageal cancer and for analyzing tissue and cancer samples to identify and confirm stomach or esophageal cancer and to determine the level of migration of such cancer cells. There remains a need for compositions which can specifically target stomach and esophageal cancer cells. There is a need for imaging agents which can specifically bind to stomach and esophageal cancer cells. There is a need for improved methods of imaging stomach and esophageal cancer cells. There is a need for therapeutic agents which can specifically bind to stomach and esophageal cancer cells. There is a need for improved methods of treating individuals who are suspected of suffering from stomach or esophageal cancer cells, especially individuals who are suspected of suffering from metastasis of stomach or esophageal cancer cells. There is a need for vaccine composition to treat and prevent metastasized stomach and esophageal cancer. There is a need for therapeutic agents which can specifically deliver gene therapeutics, antisense compounds and other drugs to stomach and esophageal cancer cells.